Old article, but interesting trick to play with. May not work anymore... http://www.diggfish.com/hiding-data-files-within-the-images/ tsp
This still works but the guy on the other side of the internet has to rename the file manually so it's not really handy.
It's called steganography. Pretty popular communication tool for terrorists -- probably not that specific method in the link but the same idea.
hiding data inside of an image is not new. i first heard about doing it many years ago, although the method described to me was different from this one. you can also hide messages in spam, like this: www.spammimic.com/encode.shtml tsp
Yeah hiding things inside images has been around for a long long time. For example, right click and save my avatar (should be called vava.gif) to your computer. Then rename it to vava.rar and uncompress it with winrar or similar.
You can hide data inside any file that can be modified without causing an error (images, wavs etc). As far as I know, you simply take a bitstream of the source and place one bit at a time into the least significant bit of each byte in the target, thereby changing the target very slightly (but not so much as to be noticable).
use dos to attatch data after anything with a header/footer. loadsa ppl use RAR's as files only read them starting from the header, so if you have an image/w.e. the image works too. RAR's inside JPG's is common, but as i said, anything with a header works too. dos commands ftw!
